Question for lifters?

Alright so I've been hearing some weird stuff at the gym. Which frankly seems like bs or bro science to me , but I haven't lifted long enough to know everything so I thought I'd ask you guys about it.

So there are two things I wanna know about

1) is it true that if you dont strech after lifting you can get some sort if cancer ( a trainer at my gym told me this , seems like bs to me)

2) some people lift in a very strange way. They keep adding weight to every set they do.
For example if they have four sets
first set is 15kg
Second is 18/19kg
Third is like 20kg
And fourth would be like a 25 kg


This seems like a very weird way of lifting. Is this a legit way to gain muscle? Should you increase your weight every set?

Are any of the above mentioned two true?
Updates
+1 y
I actually thought people wouldn't answer thinking that his was a troll question , cause the first one sounds so dumb ! I can't believe the guy who told me this was a Personal Trainer :/

Thanks for everybody who answered
Question for lifters?
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