Idena mining reward per day is 6 idena, will the reward be any less than now ? Will Idena be able to list on major exchanges?
There is fixed 51840 DNA per day per all nodes. So more nodes = lower rewards for each node.
If you have more basic questions you will find answers very fast here:
https://idena.io/?view=faq
https://idena.site/idena-introduction/
https://idena.site/faq_tutorials.php#answer4
You can buy/sell IDENA on Qtrade - quite good exchange registered in US. Vitex and huobi. In terms of major exchanges - there are rumors (rumors only) about huobi listing. We are close to lauch of ETH bridge that will allow idena to be listed on all ETH dexes.