To remove someone from your freindlist open the "Friends" tab in the middle of the right bar. Then open the second tab and find a friend you want to remove. Tap on the cross opposite the game avatar and confirm removing.

Whenever you update your game to the latest version you may come across a trouble visiting those friends of yours who haven't updated yet. Please, do not worry. The limitation will be eliminated as soon as your friends get the latest version installed.

Sometimes friend codes don't give a reward. It is the feature of the game. 
There is a certain amount of luck involved. 
Sometimes you get up to 5 Diamonds. 

There are two types of horses in the game.
The collection and the quest ones.
The elder gypsy gives you the quest one. Thus, according to the game rules it disappears.

Now you can ask a friend for a completed collection item. To do that, open a room, for example Hunting room, in an appeared offer window choose one of 5 collection items you need. Note, that you can do this only when you open the room for the first time!

Note that effect never goes to the Inventory. Check the right side of the screen. You will  observe a relative icon when it is working.
That is how Artifacts are in effect: you collect it, charge it when you get all the items, it dissapears from your collections but you get some benefits for the certain period of time in the game.

The creatures still show up in the game, even after the offer is over. This is a game feature and it is done to make the game more colorful and vivid. Whenever the special offer is over, game creatures stop dropping any bonuses though you can still banish them. 

“Energy” is what you use when you are exploring rooms. “Strength” is used for friends' visits only.

Energy

Energy is used each time you explore a room and you are given 30 energy points when you start the game.

Energy tab is located in the top center of your game screen and you can see a clock under it which gives you one energy point each time it hits zero.

Each time you level up the maximum energy increases by 10 and you get a complete energy tab refill each time you level up.

If you run out of energy it will regenerate by one energy point per three minutes.

How to obtain more energy - You can obtain energy points in a few ways. You can let it regenerate over time, activate the relative charms, or you can purchase meals with diamonds in the game store: Chocolate, Cup of Coffee, English Breakfast, etc.

Strength

Strength is used each time you visit a friend and you are given 25 strength points when you start the game.

Each time you level up the maximum strength increases by 10 and you get complete strength tab refill.

Each time you give your friend hints you spend 10 strength points.

If you run out of strength it will regenerate by one strength point every three minutes. You will not be able to visit friends until you have enough strength points to help them out.

How to obtain more strength - You can obtain strength points by waiting until it regenerates by itself or by using relative items: Expander, Dumbbels, Barbell, etc.

In case a friend was deleted, you need to wait for 30 days. Then you can add him/her again.
This temporary limitation is the game feature. To add a player again, choose Friend button, go to Add Friends tab and you will be able to add friends. Besides you can share friend codes with each other to become friends.

When you open a Room for the first time you can see an offer on the right side of your screen according to which you should give a certain number of items/diamonds every time you want to explore a room. When the offer is over, you won't have to pay items/diamonds anymore.  

Please, note that the offer will last for a week and there is no way to ignore it. If you fulfill the requirements of the offer in time, you will get a reward. This rule refers to Hunting Room, Hallway and Japaneese garden.

According to the gameplay you should pay each time you want to explore Fortune-Telling room, Room 51, Sakura room, Oceanic room, and Laboratory.

To redeem the code go to Friends tab -> Services -> Gift code and insert the given code.

Once you have all five required items in a collection you will also have to have the correct number of collectibles required to charge the box. Once this is done, you will earn coins and/or experience points reward as well as a special item to be used in the game.