Yes. Ekasana, Upvas and Ayambil can be observed during Vees Sthanak tap, but the exact rules may vary between Digambar and Shwetambar traditions and by local guidance from your guru or community.

• Ekasana: consuming food only once in the day. The timing and allowed foods can vary, but the principle is a single, simple meal with restraint.
• Upvas: a fast with specific restrictions. This often means restricting certain foods or skipping meals while keeping to a disciplined routine. Details (which foods, how long) differ by tradition and guidance.
• Ayambil: a vrata in which one meals’ worth of food is taken with particular care and minimal quantity, often prepared in a specific manner with emphasis on non-violence and contemplation. The number of ingredients and the manner of preparation can differ by tradition and region.

Important points:

• There are notable differences between Digambar and Shwetambar interpretations. Some communities emphasize stricter fasting rules, while others focus on the spirit of self-control, mindfulness, and non-attachment.
• For exact procedures, timings, allowed/forbidden foods, and the number of days (if Ayambil is practiced for multiple days), consult your local guru or the tradition-specific rules your community follows.

If you’d like, tell me your specific tradition (Digambar or Shwetambar) and your locality, and I can give a more targeted, tradition-aligned outline.