Requirements to turn the “Achievements” statue golden

Since you are already familiar with the PC version, I'll go into the other ones:

iPhone version

It contains the entire campaign, as well as different achievements (also different Easter eggs, such as what happen if you scroll down the achievement listing continuously). The puzzles are mainly the same as well.

• Doesn't have survival mode.
• Doesn't come with most of the bonus games (including the plant garden, the tree of wisdom, as well as the Zombiequarium minigame)
  • These must be purchased with either in-game coins or with real money using microtransactions
  • All Mini-game packs can be purchased for 50,000 coins each, the I, Zombie game pack for 150,000 coins, the Vasebreaker game pack for 150,000 coins, and the Last Stand game pack for 100,000 coins.

iPad version

Identical to the iPhone version, except it now includes the Survival mode. However, now it includes a new way to improve the power of your cobb plants (by putting butter on enemies first). This is making use of the iPad multitouch mode of up to 11 touches at once (think launching multiple walnut in walnut bowling at once). Still no zen garden.

Read more on the Wiki here: Game versions of Plants vs. Zombies

At first, the credits available to you in the single player campaign is limited to that from missions alone. However, once you've fully maxed out either the zerg or protoss research trees, you gain the ability to trade any future research points into 10k worth of credits.

There have been mentions of a glitch with the way the game handles this: if you replay a mission you've already beaten and acquire protoss / zerg research points within that mission, it is possible to get the Moebius foundation to "purchase research samples" from you, even though you failed to increase your net points (you already got them once). In this way, you can accrue as many credits as you need, and can buy all the armory upgrades in a single playthrough.

Update: This method has since been patched.

As of now, the best way to earn the armory achievements is to play the campaign multiple times, selecting different upgrades on each playthrough, as achievements are shared across all campaigns.