OK, @RameshMukka , what I'm suggesting is purely to enable access to a customer's environment.
So, let's say that my company, Company A, has Company B as a tenancy, they are able to access their systems through the tenancy administration options (I don't know those links, sorry).
We could create any users required for Company B, and we should be able to use our Company A access to manage most aspects of their tenancy through the tenancy administration panels.
However, sometimes we need to perform or test 'local' actions, as a 'local' user. So what I have described to you, above, is you creating another version of yourself at Company B. It won't have a company email address (just something like rameshm@companyb.onmicrosoft.com ), but it will allow you to perform testing and trialling of stuff at Company B using any facilities that will work on a free licence (or paid if they're willing to pay for it!).
Flow has free access, so you can create the account on their tenancy, then log in to Microsoft Power Automate with it, too.
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Separately ... and I can't stress this enough ... completely separately. I'm saying this so that you aren't conflating what I'm about to say with what I said above ... 😉
When you sign up for Microsoft Power Automate, you must pick a location. This location is likely something to do with both local privacy / data protection laws, and probably also CDN style replication (or caching) of data for Microsoft's data ... which includes your flows or those of your client/tenant.
So this could mean that India and the US is currently browsing Flow just dandy. Where-as the UK and Australian could be having issues.
I'm not 100% sure on all of this, but (given the current issues) it seems about right.