Apple's (NASDAQ:AAPL) second-quarter earnings release on Tuesday will likely include some very useful information for investors, including a likely look at the severity of a rare year-over-year decline in revenue, as well as a window into what management expects for the next quarter. But, as usual, I'm most excited about the earnings call following the release. During the call, the company will provide commentary on the quarter's results, as well as hopefully answer these three questions:

1. Will iPhone sales return to growth soon?
Apple's guidance for Q2 implied about an 11% year-over-year decline in revenue compared to the year-ago quarter. With iPhone sales accounting for about 68% of the company's total revenue, this guidance clearly suggests management expects iPhone sales to decline during the quarter.

Image source: Apple.

During the company's first-quarter earnings call (via a Thomson Reuters transcript), Apple management blamed the expected year-over-year decline in iPhone sales on a tough comparison in the year-ago quarter, as well as unfavorable currency changes.

Apple CEO Tim Cook said Q2, in particular, is likely the "toughest compare" for the year.

We believe it's the toughest compare because of the year ago quarter also had catch up in it from Q1. If you recall, we were heavily supply constrained throughout the whole of Q1, and so some of that demand moved into Q2.

Hopefully, Cook will provide an update on how the company views iPhone sales comparisons for the rest of the year, and -- if we're lucky -- maybe a glimpse at his long-term view for iPhone sales.

2. How is the iPhone SE performing in Greater China?
Apple's March-introduced iPhone SE was a huge departure from its typical new iPhones. For the first time ever, the company basically went back and revamped one of its older iPhones, relaunching it with a new name and new guts. Launched between Apple's usual iPhone announcements for flagship versions of the smartphone, the company appears to be aiming to create a more-competitive offering for more price-sensitive markets -- markets like Greater China.

iPhone SE's guts are no joke. Image source: Apple. 

It's not surprising Apple wanted to launch an iPhone that would appeal specifically to Greater China. In the company's most-recent quarter, Greater China represented a whopping 24% of the Apple's revenue -- second only to its Americas market, which stands at 38% of revenue.

Some early data when iPhone SE was launched suggested the new phone is, indeed, a hit in China. Three days before shipments of the device began, Apple raked in 3.4 million in pre-orders from non-Apple retailers for the iPhone SE, according to a report from CNBC.

Perhaps Apple will provide some insight into how well the new phone is holding up in the company's important Greater China market.

3. How's the quality of Apple's pipeline?
Finally, investors will want to look for an update from management on the company's confidence in its pipeline.

Given Apple's love of secrecy about future products, don't expect anything very detailed. But Apple has provided vague, yet useful, information about its pipeline in the past. For instance, ahead of the Apple Watch, the company made it very clear it would soon launch a product in a "new category," and the CEO even was as specific as to note that he thought wearables would become a "very key branch of the tree." 

Apple Watch. Image source: Apple.

As Apple struggles to grow revenue, could Cook tease investors with some hints about the company's pipeline? At the very least, investors should look for the CEO to express high confidence in its upcoming products.

Apple reports results for its second fiscal quarter after market close on Tuesday, April 26. The company will host a live conference call to discuss the results in a Q&A session with analysts at 2:00 p.m. PST.