If you have icloud then you can transfer them.
Yes there is a way, you can just go to the backup/system operating system and delete/archive the update, but its only a limited amount of time though, and to be honest with most software, its very hard to downgrade an update, that requires professional skills, but there is a way. If you want try looking up how to downgrade an update for ios on google search and that should help you.
D.) Write down the error message and research the cause based on the message.
Answer: Add more cells in series.
Explanation:
Adding more cells in series will add voltage which will increase the power.
