Is it possible for tor exit nodes, or all nodes to have multiple ip addresses say 2 billion so that they alternate each user request through those ip addresses because presently tor addresses are blacklisted as spam or mistaken for bots, rendering it impossible to browse the internet anonymously.
In short, no. Additionally, having separate IP addresses would not keep Tor from being blacklisted as spam or mistaken for bots.
A server can have multiple Internet connections, and therefore have multiple IP addresses, but each instance of Tor can only run on 1 IPv4 address and 1 IPv6 address. The only way for Tor to use a separate IP address for each person would be if there was exactly 1 Tor exit relay for each person. However, this would break anonymity as individual people could be traced to their individual exit node.
Tor relays publish their IP addresses so clients can connect. It doesn't matter if there are 2 addresses or 2 billion addresses. If somebody wants to blacklist Tor, or mark Tor users as bots, they can easily do so no matter how many addresses Tor has.
rendering it impossible to browse the Internet anonymously.
I don't understand what you mean here. I have used Tor for quite some time. Yes, some websites block Tor, and most websites require Captcha challenges, but it is far from "impossible" to use Tor to browse the Internet.
"2 billion" is infact about half of the entire ipv4 space, so the numbers are unrealistic.
>>> log(2000000000,2) 30.897352853986263
If you had a large set of IP addresses that were from different ranges, not all in one subnet, then you could try this but eventually they'd all get blacklisted.
blacklisted as spam or mistaken for bots
This isn't actually a misclassification, Tor gets abused as crawlers/scrapers and comment spam and this is essentially where your plan falls apart.
People will still abuse IPs from your set, slowly they'll get blacklisted and worse they won't all be listed as Tor exit nodes, meaning you'll be blamed for all the abusive traffic that is sent over them and will have a hard time proving it wasn't you.
Tor Exit addresses being public does two things:
It makes it easy for people who simply do not want to handle, or to handle differently, Tor traffic to classify Tor traffic from not Tor traffic in a heuristic way.
It shows that the traffic is from a Tor Exit node, helping to protect the Exit node operator from the actions of Tor users.
So you could attempt this but it would raise suspicion about your relay and you might end up on the hook for what Tor users use it for and eventually your pool of IPs would get blacklisted anyway.