Yes — Ii-frames ze-MP3 zii-blocks ezinobungakanani obumiselweyo, ngoko ukutywina kuwela kumda we-frame kwaye abaphawuli bokudlala abangena-thuba ababuyi kuqhubeka nokuphinda bakhowudi. It is worth knowing before you overwrite an original you might need again.
No. Cima MP3 is free without an account, and nothing is added to the audio. The upload and the result are deleted automatically about 24 hours after the job, which leaves time to download the result.