Abraham was tried and proved to demonstrate his obedience to God. Faith is always obedient, and obedience proves the presence of true faith.
You may have a proving in the near future; you may be in the middle of one. It will refine you. It will bring you back to full faith and trust. It may help you to surrender something to the Lord that you are better off without. Trust him: if you have got real faith and saving faith, it will lead to obedience.
How old was Abraham and how old was Isaac? It's difficult to say precisely. Isaac was born when Abraham was just past 100, and now he is big enough to carry all the wood. Some people think he was 19, but he was certainly no small lad. The Jewish historian Josephus thought he was about 26 years old, that would make Abraham 126. He was somewhere between 19 and 30, so 26 is not a bad estimation. You can imagine a grown man letting an aged man bind him. Isaac too exercised faith and submitted to the command of God in this matter. Abraham still must face a proving from God even at that age. Not only young believers are proved or even middle-aged believers, but ancient believers also may face a great proving, and Abraham most certainly did.