Haiz, Istihaazah & Nifaas

Tawbah

Q: If a female who is menstruating makes a mistake and cannot pray the prayer of repentance so she repents in her heart by asking for forgiveness and saying sorry and at the end says ameen, does it count or do you have to read /say something a surah or something in the beginning as well?

Not experiencing haidh

Q: There is one girl. Her age is around 25. She is still not matured as she didn't get haidh yet. Is is because Allah Ta'ala's la'nat is on her because she consulted with many Doctors and hakeems but nothing happened. Please let me know what Allah Ta'ala says regarding this issue.

Irregular bleeding

Q: If my wife is always having periods for 5 days. After 5 days can we can do 'intercourse'? Last week after 5 days, after confirming that there is no more bleeding and no signs of blood, we did. But after 2/3 hours suddenly bleeding starts, this was the first time it happened. What does Shari'ah says about it? I can't explain my question much but please give me a detailed answer as we are very concerned about this. We don't want to commit any sin.