As said the title;
Is it possible to know if two or more addresses are related to one wallet? and if from transactions i can figure possible connection (same wallet) between addresses.
I post this here because i think it's a beginner question, no?
Yes, it is possible. The most simple example I can think of is this. Suppose you have 1 BTC and you send 0.6 BTC to your friend. In this case, you have a change of 0.4 BTC that goes to your change address, the other 0.6 BTC goes to your friend. Now you have 2 addressess: the first one with 0 BTC and the second one with 0.4 BTC that anyone knows are belong to the same person.
There is another example. Suppose you have many addressess with small amounts of BTC in your wallet. Let's say you have 10 addresses with 0.1 BTC each. But you need to send 0.91 BTC to your friend. In this case all your 0.1 amounts are gathered in 1 transaction and sent to your freind's address. Everyone will see that you used 10 addresses to complete that transaction. You will also receive 0.09 BTC to your change address which will also be seen in the blockchain. Now everyone will know that those 11 addresses belong to the same person.