Also you'll likely end up infertile.
It's not as simple as "experimenting" with TRT. Exogenous testosterone will begin diminishing your natural testosterone production immediately. In theory there are ways to counteract this, but in practice it's not guaranteed that someone can ever discontinue TRT once they've started. Even those who rebound may not return to their original, pre-TRT levels.
Testosterone is also interconnected with other hormone systems, which will also be disrupted by TRT. For many, TRT turns into a game of adjusting various medications up or down to try to get back to how they felt pre-TRT.
No, absolutely not.
The size of your testicles is in no way indicative of your testosterone production.
While a shorter period of use generally has a higher chance of your natural production restarting after ceasing exogenous testosterone, your natural production of testosterone shuts down immediately with the introduction of exogenous testosterone.
Testicle shrinkage is unarguable a side effect of exogenous supplementation. How is that not a good marker for your production shutdown? If there’s a good explanation, you’re not being very clear about it at all.