diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0993e3f88..ed37b7e94 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,17 +5,26 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased v4.0.0]
+## [v4.0.0-beta]
+## Changes
 
 ### Added
-- [*BREAKING*] `implementation`, `override` macros: [78](https://github.com/Brushfam/openbrush-contracts/pull/78) 
-- [*BREAKING*] `storage_item` macro, new OB feature: `Upgradeable`, which implements `set_code_hash` functionality [99](https://github.com/Brushfam/openbrush-contracts/pull/99)
-- `UI` tests [77](https://github.com/Brushfam/openbrush-contracts/pull/77)
-- `openbrush::accessors` macro for automatic generation of getters/setters for storage items: [66](https://github.com/Brushfam/openbrush-contracts/pull/66) and [61](https://github.com/Brushfam/openbrush-contracts/pull/61)
+- [*BREAKING*] `implementation`, `override`, `default_impl` macros: [#78](https://github.com/Brushfam/openbrush-contracts/pull/78) 
+- [*BREAKING*] `storage_item` macro, which implements `#[ink::storage_item]` macro, but also allows to make field of struct upgradeable by using `#[lazy]` attribute. For all fields that
+ are either `Lazy`/`Mapping`/`MultiMapping` is generated it's own constant storage key. Also it allows OpenBrush to work correctly with every default implementation [#99](https://github.com/Brushfam/openbrush-contracts/pull/99)
+- New OB feature: `Upgradeable`, which implements `set_code_hash` functionality [#99](https://github.com/Brushfam/openbrush-contracts/pull/99)
+- `UI` tests for testing different scenarios for macros [#77](https://github.com/Brushfam/openbrush-contracts/pull/77)
+- `openbrush::accessors` macro for automatic generation of getters/setters for storage items: [#66](https://github.com/Brushfam/openbrush-contracts/pull/66) and [61](https://github.com/Brushfam/openbrush-contracts/pull/61)
 
 ### Removed
-- [*BREAKING*] `min_specilization`, now openbrush is `stable`: [78](https://github.com/Brushfam/openbrush-contracts/pull/78)
-- `ZERO_ADDRESS`, now using `Option<AccountId>` instead: [98](https://github.com/Brushfam/openbrush-contracts/pull/98)
+- [*BREAKING*] `upgradeable_storage` macro, `OccupyStorage` trait [#99](https://github.com/Brushfam/openbrush-contracts/pull/99)
+- [*BREAKING*] `min_specilization`, now OpenBrush can be used with `stable` toolchain: [#78](https://github.com/Brushfam/openbrush-contracts/pull/78)
+- [*BREAKING*] `ZERO_ADDRESS`, now using `Option<AccountId>` instead: [#98](https://github.com/Brushfam/openbrush-contracts/pull/98)
+
+### Changed
+
+- [*BREAKING*] Now every field in OpenBrush's types that is not read/written directly in storage, is wrapped in `Lazy`, so all the types in OpenBrush can be considered upgradeable: [#99](https://github.com/Brushfam/openbrush-contracts/pull/99)
 
 ### Fixed
 - Fixed reentrancy guard problem: [#88](https://github.com/Brushfam/openbrush-contracts/pull/88)
+- Updated reentrancy example: [#108](https://github.com/Brushfam/openbrush-contracts/pull/108)
\ No newline at end of file
diff --git a/examples/payment_splitter/lib.rs b/examples/payment_splitter/lib.rs
index 9247fb5b6..ccf008750 100644
--- a/examples/payment_splitter/lib.rs
+++ b/examples/payment_splitter/lib.rs
@@ -3,7 +3,6 @@
 #[openbrush::implementation(PaymentSplitter)]
 #[openbrush::contract]
 pub mod my_payment_splitter {
-    use ink::prelude::vec::Vec;
     use openbrush::traits::Storage;
 
     #[ink(storage)]
diff --git a/examples/reentrancy_guard/contracts/flip_on_me/lib.rs b/examples/reentrancy_guard/contracts/flip_on_me/lib.rs
index 03c343229..340b7bdc6 100644
--- a/examples/reentrancy_guard/contracts/flip_on_me/lib.rs
+++ b/examples/reentrancy_guard/contracts/flip_on_me/lib.rs
@@ -1,9 +1,13 @@
 #![cfg_attr(not(feature = "std"), no_std, no_main)]
 
+pub use openbrush::examples::contracts::reentrancy_guard::flip_on_me::*;
+
 #[openbrush::contract]
 pub mod flip_on_me {
+    use flipper::traits::flipper::*;
     use flipper::traits::flip_on_me::*;
-    use ink::codegen::Env;
+    use ink::env::CallFlags;
+    use openbrush::traits::DefaultEnv;
 
     #[ink(storage)]
     #[derive(Default)]
@@ -17,16 +21,14 @@ pub mod flip_on_me {
     }
 
     impl FlipOnMe for FlipOnMeContract {
-        #[ink(message)]
-        fn flip_on_me(&mut self) -> Result<(), ReentrancyGuardError> {
-            let caller = self.env().caller();
-            self.flip_on_target(caller)
-        }
-
         #[ink(message)]
         fn flip_on_target(&mut self, callee: AccountId) -> Result<(), ReentrancyGuardError> {
             // This method does a cross-contract call to caller contract and calls the `flip` method.
-            flipper::traits::flipper::FlipperRef::flip(&callee)
+            FlipperRef::flip_builder(&callee)
+                .call_flags(CallFlags::default().set_allow_reentry(true))
+                .invoke()
+                .unwrap();
+            Ok(())
         }
     }
 }
diff --git a/examples/reentrancy_guard/contracts/flipper/lib.rs b/examples/reentrancy_guard/contracts/flipper/lib.rs
index d795bfcc0..581117019 100644
--- a/examples/reentrancy_guard/contracts/flipper/lib.rs
+++ b/examples/reentrancy_guard/contracts/flipper/lib.rs
@@ -1,12 +1,18 @@
 #![cfg_attr(not(feature = "std"), no_std, no_main)]
 
+pub use openbrush::examples::contracts::reentrancy_guard::my_flipper_guard::*;
+
 #[openbrush::contract]
 pub mod my_flipper_guard {
     use flipper::traits::flipper::*;
+    use flipper::traits::flip_on_me::*;
     use openbrush::{
         modifiers,
         traits::Storage,
     };
+    use ink::env::CallFlags;
+    use openbrush::traits::DefaultEnv;
+
 
     #[ink(storage)]
     #[derive(Default, Storage)]
@@ -43,7 +49,11 @@ pub mod my_flipper_guard {
             // Callee contract during execution of `flip_on_me` will call `flip` of this contract.
             // `call_flip_on_me` and `flip` are marked with `non_reentrant` modifier. It means,
             // that call of `flip` after `call_flip_on_me` must fail.
-            flipper::traits::flip_on_me::FlipOnMeRef::flip_on_me(&callee)
+            FlipOnMeRef::flip_on_target_builder(&callee, Self::env().account_id())
+                .call_flags(CallFlags::default().set_allow_reentry(true))
+                .invoke()
+                .unwrap();
+            Ok(())
         }
     }
 }
diff --git a/examples/reentrancy_guard/traits/flip_on_me.rs b/examples/reentrancy_guard/traits/flip_on_me.rs
index 1472c260b..74e1f1a1c 100644
--- a/examples/reentrancy_guard/traits/flip_on_me.rs
+++ b/examples/reentrancy_guard/traits/flip_on_me.rs
@@ -6,9 +6,6 @@ pub type FlipOnMeRef = dyn FlipOnMe;
 
 #[openbrush::trait_definition]
 pub trait FlipOnMe {
-    #[ink(message)]
-    fn flip_on_me(&mut self) -> Result<(), ReentrancyGuardError>;
-
     #[ink(message)]
     fn flip_on_target(&mut self, callee: AccountId) -> Result<(), ReentrancyGuardError>;
 }
diff --git a/examples/timelock_controller/lib.rs b/examples/timelock_controller/lib.rs
index 77053bcf6..b1f4d312c 100644
--- a/examples/timelock_controller/lib.rs
+++ b/examples/timelock_controller/lib.rs
@@ -3,7 +3,6 @@
 #[openbrush::implementation(AccessControl, TimelockController)]
 #[openbrush::contract]
 pub mod my_timelock_controller {
-    use ink::prelude::vec::Vec;
     use openbrush::traits::Storage;
 
     #[ink(storage)]