Why should the order of Chebyshev be less than 1006? I've seen this statement in two places

Library Questions
1

Engorgio: An Arbitrary-Precision Unbounded-Size Hybrid
Encrypted Database via Quantized Fully Homomorphic Encryption

And

2

Because it is basically the last degree supported for a given multiplicative depth (11). See openfhe-development/src/pke/examples/FUNCTION_EVALUATION.md at main · openfheorg/openfhe-development · GitHub for more information.

3

If the number of oder is greater than 2031, is it also okay to set the depth a bit larger?like 13 or 14？

4

Yes, in principle you can set whatever degree you want, as long as the specified depth supports it. You just need to be careful to update the tables in ckksrns-utils.cpp if you plan to use the internal functions for a degree larger than 2031.