Like any yeast, dry wine yeast can benefit from additional nutrients. I have a package of dry yeast that is 6 months past its expiration date.

Can I still expect it to work?

Although the yeast might still be viable and active, there is no guarantee that it will perform as well as yeast within its expiration date.

During rehydration the cell membrane undergoes changes which can be lethal to yeast. In order to reconstitute the yeast as gently as possible (and minimize/avoid any damage) yeast producers developed specific rehydration procedures. Although most dry wine yeast will work if pitched directly, it is recommended to follow the rehydration instructions to insure the optimum performance of the yeast.

It is not a good policy to mix strains since there is too much uncertainty. Each strain has its own lag phase, growth rate, oxygen and nutrient requirements. Each strain reacts slightly different to temperature and pH. It’s very important to know the possible synergies or antagonism between the 2 yeasts as it will influence the dynamic of population. Some strains have the competitive factor or are quicker to take in the nutrients. Some are sensitive to the factor while other strains are immune to the factor. It is possible to make a 50/50 blend inoculation and within 48 hours find only 100% of one of the strains. If you are doing this to achieve more "complexity" in the final wine, a better way is to divide your juice into separate fermenters and then ferment each selected strain separately. You can determine the fermentation characteristics and flavor and aroma profile of each strain separately, and then blend the finished wine to your taste. This is a more reliable way to achieve the benefits of a mixed fermentation.

Some yeasts will be more sensitive to SO2 than other yeasts. In general high SO2 additions may be used to stop the yeast fermentation once the fermentation is complete and the yeast are already in a weakened state.

It is possible, but the important factors are air and moisture. If you can vacuum seal the yeast then this would be ideal, otherwise a re-sealed pack should be used quickly as the cells will lose activity in the presence of air and water. Pressing a pack tightly before applying the seal is not really that effective. Use opened yeast within a week to ensure good performance.

At warm fermentation temperatures, more esters and higher alcohols are produced than at colder temperatures, resulting in more fruity, floral flavors.

The pitching rate influences the lag phase and general fermentation speed as well as the flavour of the finished wine. Too low pitching rates will result in longer lag phase and higher risk of contamination as well as longer overall fermentation time (and sometimes stuck fermentations). Too high pitching rates speed up the fermentation but can lead to early autolysis.