well, you have two options then. Find an R4 cart that works on 1.4.5 or do the downgrade process.
The downgrade process is not the best, and if you don't follow the guide to the letter you risk bricking your DSi.
The official guide can't be found through the regular website anymore, the site is down and has been for a little while.
So you can get the guide by using the wayback machine to view a snapshot of it from when it was still live.
As for getting the files, you can right click the links and select to open in a new tab. Once in a new tab, you can go up to the address bar and remove all the junk before the https of the link so that you remove all the stuff related to the wayback machine and get a proper direct link.
Most of the...