If you have root you may want to use something called ACC (Advanced Charging Controller). You can use its official app, ACCA, to install it. Very customizable.

Samsung phones have an option in the battery settings called “charge protection” and it makes your phone stop charging at 85%. Look through your battery settings to see if you have a similar option.

Not without rooting it or the manufacturer including a custom option for it, but if it has adaptive charging, you can set an alarm and it will charge the phone up to 80% and then wait to charge it the rest of the way to coincide with the alarm so that it isn’t at 100% for a long time.