Should I get an interest only 30 year fix mortgage?

I'm considering an interest only 30 year fix mortgage but I'm still a bit confused. After the 10 years, will the interest rate be changed to the rate at that time, or will it still be the same as when the loan first started? If I made a large lump sum payment at the end of the 10th year, that will... show more I'm considering an interest only 30 year fix mortgage but I'm still a bit confused.

After the 10 years, will the interest rate be changed to the rate at that time, or will it still be the same as when the loan first started?

If I made a large lump sum payment at the end of the 10th year, that will reduce my principle right? But will it also lower my monthly payment?

Does it make sense to save the money that you saved (about $200 a month) and invest it (at 3-4%), and after the 10th year, use that money as a big payment towards the principal. Thereby having a low payment for the first 10 years, and for the remaining 11-30 years, a payment that is not much higher than a regular 30 year fix mortgage?

Can someone answer my first 2 questions and also tell me if my reasoning can / cannot work?
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