Reciting Durood before giving Azaan

Q: What is the basis in shariah of reciting Durood before giving the azaan? Also, when carrying out a good deed, eg, performing umrah, nafl hajj, reciting the Quraan etc, if one makes intention to pass the reward onto deceased relatives or our Prophet (Sallallahu Alayhi Wasallam), does the person himself get reward in full too?

Infants wearing short clothing

Q:

1. Regarding new born and small babies, is it permissible to make them wear clothes which do not cover the satar, e.g. short pants or sleeveless tops for a baby girl? Provided they aren't going out of the home etc.

2. If permissible, at what age should they be made to wear more modest clothing?

Istihaazah

Q: I started bleeding again after 11 days since my last haiz. Is this regarded as istihaaza? And what are the rules regarding istihazaa? When will I count
my haiz from?

Irregular bleeding

Q: I have a question, one sister recently had a miscarriage of a baby of 7 weeks, and after that during 2 weeks she has been bleeding. I know that just 10 days is the maximum a person is considered napak in the case of Haidh, and 40 days in the case of giving birth, but how is it in this case?

Also there's another sister whose Haidh has altered due to an infection called depropovera, which she used for stopping her Haidh during Hajj. Now she has been bleeding for two weeks, some days it seems that it has stopped but then it comes a lot. Her habitual days was 7 days. So which days are considered Haidh and istihadha?