Updating to 64 bit programs

64-bit spec won't take effect until you download Catalina when it's available. If you choose not to update your OS, then MS apps should continue to work fine. If you do then check with MS to see what updates are available.

The developer needs to update their software. In some cases, they will no longer support older software and you may need to purchase newer versions. But you do not need to do anything until you want to install the next OS Catalina.

You can't update what you have. You must purchase a newer version. The current choices are the one-time cost, perpetual license Office 2019, or the yearly/monthly subscription version, Office 365.

Check out the MS website. I don't know if you'll have to purchase, as it depends on the version you currently have.

Yes.

Yes, it should, Mac has been a 64-bit system forever. But there may be other factors so check the specs.

I suggest you check out LibreOffice and find out if it fills your needs. It is free.

I know it works for me.