Business upgrades

Does a business that has been diversified count as upgraded for the purpose of League elections?

Is there an increased cost to further diversifications, after the first in the same way as normal upgrades?

Thanks

No.

No, nor any increase in the cost of upgrades. Diversification costs are flat and do not affect other costs.

As a followup question - if a business is fully upgraded can it continue to be diversified?

There is no such thing as “fully upgraded”. There is no limit to the number of upgrades that you can buy.

You can continue to buy diversifications to diversify your upgrades if you so wish. It’s not cheap - but you can do it.