How far can I update iMac A1208

You’re quite welcome.

Yes, you can go straight to that version. However, I would never download any software from Softonic, or any other aggregator site. As Apple doesn’t offer it as a download, so finding a legitimate copy may be difficult.

It appears I was mistaken about Apple no longer providing a download for Lion. The link below is for the purchase of Lion.

OS X Lion (10.7) - Apple

Hello,

What is your Macintosh’s exact model number?

Choose the Apple Menu  > About This Mac

Lion (10.7.5) is the highest possible for that model. I believe it is no longer available as a download from Apple.

You’re welcome.