Iberia could be taken, and potentially defended via the Pyraneese; however in the long term I'm not sure it could be held for long. If Vienna falls then Hungary can be brought in with most of the rest of Central Europe as satalites. Exploration up the Don and Volga rivers can lead to the Ottomans holding considerable territory in Russia; but that'd be mostly trading and need constant defence. Sudan, Eritraia and Eithopia can all be brought into the Empire and Islamified. Persia is also in a weak state and could probably be taken out with enough effort so you could see some power projection in India.
An Ottoman Empire this big wouldn't be very permenent as it is indefencable and overextended however its decline would be far slower than OTL.
Iberia couldn't be taken as whole, and the only realistic way to gain for Ottomans a real foothold on the peninsula would be through vassalage, which obviously the Granadans would be the easiest choice of all. And an Ottoman foothold on Iberia will almost absolutely, if not absolutely, need an Ottoman Italy to preceed it. Though by the way, to gain an Ottoman Italy is actually rather easier than to gain an Ottoman Hungary, also it would be less of an overstretch as well, with even more interesting reward.
On Don-Volga part, I don't see the Ottomans would exert direct control on it. Most likely that, through the success of establishing Don-Volga canal it will give the Ottomans one or two more subordinate khanates that will be functioning similar to the Crimean Khanate for the Ottomans, and also a connection to Central Asia. This will be hard to achieve, but once it is achieved, then it will mean that 1) Russia is screwed, 2) direct trade links to Central Asia that will benefit all members of the Ottoman party, and 3) a Persia more vulnerable for Ottoman incursion, that a western third of it can realistically fall into Ottoman hands and will may even stay Ottoman for centuries.
I don't think Ottoman expansion into deep interior of Africa will happen without medical technology on par with OTL 19th century. And I would even suspect that there will be rather little interest for interior African expansion unless it's to counter a serious enough threat that comes from there(for example, the expanding European imperialism in the continent, if there will ever be ITTL), or if ITTL trans-Saharan trade would become much more thriving than OTL....