I'll answer the easiest ones first.

1. Stream crossings.

There was nothing to cross that needed watershoes when I did the hike. I kept my boots on and easily rockhopped the creeks, as did my friends. I used my watershoes/sandals strictly as camp shoes, and was glad I had them for that purpose (only).

2. Highest elevation on first day.

The highest elevation on the first day, going from Onion Valley to Whitney Portal, is Kearsarge Pass, at about 11,800 if memory serves. You might find this graphic representation of the hike that someone else prepared helpful -- I found it helpful on my trip: http://www.flickr.com/photos/brucelemons/5258918105/.

3. I don't know what chonies are.

4. Clothing

Here is a list of what I took. I did bring a Patagonia down sweater, and loved having it in the evenings and early mornings(used it as a pillow, too).

Top
1 Patagonia (capilene) t-shirt
1 Ex Officio long-sleeved, lightweight shirt (wind/sun protection, alternative to the t-shirt for hiking, ended up using this ALOT, sometimes over the t-shirt, sometimes by itself)
1 Icebreaker 200 long-sleeved shirt for sleeping in (too warm, though I did have a 10-degree bag which was serious overkill)
1 very light Mountain Hardware lightweight synthetic pullover, similar to this one (for evenings)worn over the t-shirt or the Icebreaker
1 Patagonia down sweater
1 waterproof/wind-resistant lightweight outer shell
1 Buff (rather than a hat) for evenings and sleeping in
1 Sun hat (critical)

Bottom
1 pair convertible pants
1 pair lightweight long underwear bottoms (for sleeping in, and also for wearing when my pants got wet in the rain/hail storm!)
1 pair shorts -- wasted weight, should not have brought
Underwear

Socks
I brought two pairs of socks and alternated. I hiked in one pair the first three days, and wore the other pair at night while the first pair dried out. I hiked in the second pair the next three days. Truth is, a third pair would have been nice. Better choice than the extra shorts.

Note, I am female and tend to run cold, and overdid it slightly. The only changes I would make on clothing is that I would not have brought the Icebreaker 200 long-sleeved shirt to sleep in, and I would ditch the extra shorts. As for a shirt to sleep in, I would have been more comfortable in a lighter layer or a t-shirt.

I did not take a day to wash my clothes, but I did wash my t-shirt 2-3 times, and wore the ex officio shirt while the t-shirt was drying. With the modern fabrics, things dry quickly.