Answer

Yes, Chaṭṭh / Aṭṭham tap can generally be done according to one’s capacity and guidance, but if you are doing it as part of a specific vidhi, niyam, festival, or guru-given instruction, then you should follow the prescribed order exactly.

Explanation

In Jain practice:

• Chaṭṭh usually refers to fasting for two days.
• Aṭṭham usually refers to fasting for three days.

If someone is doing these tapas as a personal austerity for self-purification, the sequence may depend on health, strength, and spiritual discipline.

But if it is connected with a particular observance, such as a specific ritual, vow, or instruction from a sadhu, sadhvi, or guru, then the order should not be changed casually.

Spiritual Understanding

In Jain Dharma, tap is not only about the number of fasts. The inner bhaav matters greatly:

• Reducing attachment to food
• Practicing self-control
• Maintaining peace and humility
• Avoiding pride about fasting
• Doing pratikraman, swadhyay, and dhyan with purity

Takeaway

If it is your personal tap, it may be done according to your ability. If it is part of a specific religious vidhi or niyam, follow the traditional order and ask a knowledgeable guru or elder before changing it.