Move Blog to Godaddy but as a different sub domain

Thanks for reading this,

I want to move my blog to my godaddy WP hosting server but I have few problems.

– My blog is myMainDomain.com

– On my new godaddy account I am already using a false domain as primary domain like false-domain-22.com so that the other domains which I hosted on same space should not be accessed with primary domain. Thats how they work dont know but it sucks.

– Now if I want to move my blog there, then I have simple way, I should add domain there and install WP app and it will be ready. But I dont have dedicated IP so I cant test that blog. because I have used false primary domain so I now need a dedicated ip to test the installation otherwise it will be risky to point myMainDomain.com there like that.

– Then, I decided to install my blog as a sub folder of an existing domain which already is hosted on the same new server.

– So I installed a fresh copy on my other domain,
otherdomain.com/myMainDomain

– Now I think I can test the installation with with the above url.

So my question is, Is that a good way to use the blog? I mean how will I then point myMainDomain.com to this url otherdomain.com/myMainDomain

Is it good as SEO point of view?

I dont know if that is confusing question but I am very much worried I have to move my blog within 48 hours as I have problem on first hosting. My blog has 3k daily traffic and its a web development helping blog.

Any help is highly appreciated.

Thank you!