Committing indecent acts during childhood

Q: I am a 20 year old Muslim female. In my childhood maybe up to 13 years or so, I used to involve in some physical sexual activities with some of my younger and older cousins both males and females ,in the form of a game at that time. This did not extend up to zina (the actual penetration) but touching and kissing each others body parts. Will this make my marriage (I am unmarried) in the future invalid? I want to repent from this but please tell me how to repent from the same? In order for me to repent is it obligatory to ask them also to repent from the same and is it obligatory to ask forgiveness from them. I don't remember whether at times I have asked them to involve in this act and they reluctantly did or not. Please help me out with this. I really want my marriage to be valid according to Allah.

Paying for an item in instalments

Q: My question is,"I am a young person doing my job. I suffered from crises of income. My company's policy has been changed that each worker should have a smart phone to do whatsapp of any competeter activity in the market. While I don't have that phone and I don't have the payment power to purchase that cell phone on cash. So, I decided to purchase that on installment but some persons are making me tense that it is interest.(Sood). Please guide me is it sood?

Correct spelling of names

Q: We want to know if these names are Islamically correct for our child. Also, the correct way to spell in English as our Arabic is not the best. These are the names:

Nur Addunya or Noor Addunya

Nur AlJannah or Noor Aljannah

Nur AlHayat or Noor Alhayat