I have a query regarding links from forum and blog comments. Did they have any value at all? or they can just hurt my rankings.

I want a service which can optimize my app for maximum exposure and conversions. If anybody will refer me to any then it will be very helpful.

How to know my strength and weaknesses in blogging? I mean which niche to choose and which to not.

I am literally confused right now about what to do. I can a get a backlink from another language site (other than English) and it has high DA/PA. Will it be helping my site to rank? or, can it hurt my site?

It is from a while I am seeing that inbound links are regularly disappearing. I can see it in my Google Webmasters tools account. Why it is happening? Can anybody please explain, I am really worried about right now.

What are general terms that one should focus on Search Engine Marketing in 2015 to get good conversions?

I know a few bloggers who had started their blogs about 1 year or 10 months ago. Their blogs are surprisingly getting much much more conversions and that's increasing every month. How this possible? I mean in general it takes about 2 to 3 years in avg to generate revenue for a blog. But they are not only doing it but also having sales.

I am getting the message in my Google Webmasters tool account for a site that it is having mobile usability issues. It is saying that my site is not optimized for mobile devices. What should I do?

Are there any free or paid keyword research tools present from which the Search Engine rankings can be checked??

If I use paid advertisements to get traffic to my blog the. Is it possible that Google Adsense will lower there CPC for that traffic?